Signal-translating system



July 2, 11946. B. D. LOUGHLIN SIGNAL-TRANSLATING SYSTEM 4 Sheets-Sheet 3 Filed Sept. 20, "1943 OSCILLATOR BALANCED MODULATOR ii SIGNAL SOURCE (h) INVENTOR BERNARD D. LOUGHLIN BY J J y B. D. LOUGHLiN 2,403,385

' S IGNAL-TRANSLATING SYSTEM Filed Sept. 20,1945 4 Sheets-Sheet 4 F |G.5 -Z ---1- I I l OSCILLATOR l i V (f0) v a a I m i 5 "4 9 v r V up E mog f 'fiias M PHASE I o AMPLIFIER I SIGNALS MODULATOR 0 I i 0 O I I 13 m III E i 1 SIGNAL BALANCED I "l SOURCE o MODULATOR l I X I i BERNARD D. LOUGHLIN .parison. phase-reference signal, comprising the unmodu- Patented July 2,- 1946 unit-so snares n i rins.

SIGNAL- TRAN SLATING Bernard D. Loughlim-Baysid N. assignor -by .mesne assignments, to Hazeltine Research,.1nc., Chicago, Ill., a corporationof Illinois Application September 20, 1M3, Serial No. 503,071

32 Claims. (61.173 15) .Theapresentinvention relates, ingeneralgto a l signal-translating system and is particularly di IeCtGdTlAO such a system.for'translatingan angu- 'lar-ve'locity-modulated carriensignalhaving mod ulation components determined by information to be translatedand predominantlyin a predetermined bandof frequencies. While the invention :is to: be: particularly described in connection With ;:a-phase-mod-ulation system, it is equally applicable to a frequency-modulationsystem and, accordingly, the term angular-velocity=modulated carrier, signal is used in this specification and: in the appended claims to include the modulated carrier signal translated in each such systel'n,

Ina phase-modulation system it is desirable to it have at the receiver a phase-reference signal'representingthe absolute phase of the carrier com-- ponent of the receivedmodulated"carrier signal.

, provide-an iimproved angular-velocity-modulatecl carrier signal=translating system Which. is not subj ect to ".0116" or more of the above-mentioned limitations of prior art arrangements.

i It isanother object of t the invention to Provide an improved; signal-translating-system for translat-ing over-a-single channel an angular-velocity modulated carrier signal and. a" suitable reference Where such a reference signal is available; all of the modulation 'components of the received si nal maybe derived directly by. a methodiof'comln'certain tprior. art arrangements "a lated carriersignal, is transmitted to the receiver .over one channel While the modulatedcarriersigl nal is transmitted thereto over a separate and independent channel. Although such-arrangements provide the desired phase-reference signal,

they require at least two transmitting channels Which, for many installations, is an undesirable limitation.

Other prior art arrangementsutilize. some harmonic or subharmoniciof the original carrier sigu nal 'as a reference whichistransmitted over a single channel along With the modulated carrier signal and separated therefrom at the receiver.

However; these other arrangements are subject to the limitation that the reference signal and modulated carrier. signal are widely separated in the frequency spectrum. This is undesirable since the Wave propagation characteristics of a trans-.

mission channel are frequently quite different for signals of widelylseparated frequencies, which eff ect introduces. distortion into thewdetected signal.

-Sti11 otherarrangements utilizea reference osf cillator at the receiver, synchronized from the transmittento supply a phase-reference signal.

Obviously, such arrangements are objectionable in that they require-a duplication of, equipments and introduce an exacting synchronizing :problem.

Arrangements have also been proposed which include i a sharpl selective filter for selecting a isignalhaving the average phase of a received phase-modulatedsignal, the signal so selected be signal.

It is a specificcbiect of the invention toprov-ide an improved signal-translating system for translating over a single channel a phase-modulated carrier signal and a. phase reference signal.

:Inaccordance 'With the invention, a -signaltranslating system comprises means for supplying .-a first signal'and: means for effectively supplying a second signal, the second signal: comprising a pair of signal components havingpredetermined phase relations with reference to, the first signal andbeing individually spaced. therefrom in the frequency spectrum by: equal and opposite values.

This systemealso includes, means for modulating theangular velocity of one of the firstland second signals in accordance with information .tobe transmittedlto develop almodulated carrier sig 'nal having predominant modulation. components within a modulation band that is located onlyin a portion of the frequency spectrum adjacent its j carrier frequency. Thewidth of. one modulation sideband thereof is less than one of. the aforesaid values. Further, the system includes: a..signal translating channel having input andoutput ter- .minals and means for applying to t'he input terminals thereof the. modulated-carrier signal and the other one of the -first and l second signals.

'hdditional-ly, means are coupled to the output terminalsforutilizing the modulated carrier signaland the other one of the first :andsecond sig'. nals to derive the modulation components;

Also in accordance with the invention, a signal- .translatingmsystem comprises'means for supplying -afirst-signal-and means for effectively supplying a secondAsignal, the-second signal comprising -apair of signal components havingpredetermined phase relations with reference to the first-mentioned signal and; being 1 individually spaced therefrom in the frequency spectrum by equal and opposite values. The system also includes means for modulating the angular velocity of one of the aforementioned first and second signals in accordance with information to be transmitted to develop a modulated carrier signal having predominant modulation components within a modulation band located only in a portion of the frequency spectrum which is adjacent its carrier frequency, the width of one modulation sideband thereof being less than one of the aforesaid values. Further, the system includes a signal-translating channel and means for applying to the channel the modulated carrier signal and the other one of the aforesaid signals.

Also in accordance with the invention, a receiver is provided in a system for translating a composite signal which includes a first signal and a second signal, the second signal including a pair of signal components having predetermined phase relations with reference to the first signal and being individually spaced therefrom in the frequency spectrum by equal and opposite values. Also, one of the first and second signals is angular-velocity-modulated in accordance with information to be translated so as to provide a modulated carrier signal having predominant modulation components within a modulation band located only in a portion of the frequency spectrum which is adjacent its carrier frequency, the width of one modulation sideband thereof being less than one of the aforesaid values. The receiver comprises a pair of input terminals for receiving the composite signal, frequency-selective means coupled to the input terminals for individually separating the modulated carrier signal and, the other one of the first and second signals, and means coupled to the frequencyselec'tive means for utilizing the separated signals to derive the modulation components.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawings, and its scope will be pointed out in the appended claims.

' Referring to the drawings, Fig. 1 is a schematic circuit diagram of a complete signal-translating system in accordance with the invention; Fig. 2 isa graph utilized in explaining the operation of the system of Fig. 1; Figs. 3, 4 and 5 represent modifications of a portion of the signal-translating system of Fig. 1; and Figs. 3a to 30, Fig. 4a and Figs. 5a and 51) comprise graphs used in describing the operation of the arrangements Figs. 3, 4 and 5, respectively.

Referring now more particularly to Fig. 1 of the drawings; there is represented schematically a complete signal-translating system, in accordance with the invention, composed of elements which, individually, are of well-known construction and design. As represented, the system comprises a sending station Ill and a receiving station II, interconnected by a single signal-translating. channel l2 having input terminals l3, l3 and output terminals I l, Hi. Channel l2 may be a direct Wire connection as, for example, a telephone cable, or it may consist of a conventional radio link. The sending station includes means for supplying an angular-velocity-modulated carrier signal having modulation components determined by information to be translated and predominantly in a predetermined band of frequencies. This means comprises an oscillator l having a mean operating frequency f for supplying a carrier signal to be modulated, a source of phase-modulating signals i6 representing the information to be translated, and a phase modulator 'I'? having one input circuit coupled to oscillator l5 and another input circuit coupled to signal source It.

There is also included in the sending station means for supplying a pair of reference-signal components having predetermined phase relations with reference to'the carrier signal applied to phase modulator ll. means for supplying a second carrier signal having predetermined phase and frequency relations with reference to the first carrier signal, namely, that applied to modulator ll. It is preferred that the second carrier signal have substantially the same frequency and phase as that of the first carrier signal and, consequently, it is expedient to derive the second carrier signal directly from oscillator I5, as illustrated, although an auxiliary oscillator may be provided if desired. The means for supplying a pair of referencesignal components also comprises a signal source it which supplies a modulating signal having a predetermined frequency f1, to be defined more particularly hereinafter, and a balanced amplitude modulator it having one input circuit coupled to oscillator i5 and another input circuit coupled to signal source iii. The output circuit of modulator i9 is arranged to select only the upper and lower sideband components of amplitude modulation which are utilized as the reference-signal components, the second carrier Signal being suppressed.

Other information, in addition to that represented by signal source iii, may also be transmitted from sending station H) to receiving station I! over the channel [2. For this purpose, means, comprising an amplitude modulator 29, are included in the sending station for modulating each of the reference-signal components produced in balanced modulator i9 in accordance with such additional information. Modulator 2@ has one input circuit which is coupled to balanced modulator i9 and another input circuit coupled to a signal source 2!, representing the additional information to be translated. The frequencies of the signals developed by source 2! are included in a predetermined band of frequencies, defined more particularly hereinafter.

The output circuits of modulators I1 and 26 are connected to the input circuit of a combining amplifier 22. The output circuit of this amplifier, in turn, is connected to input terminals l3, I3 of signal-translating channel I2, thereby to provide means for applying the phase-modulated carrier signal developed in unit 11 and the amplitude-modulated reference-signal components developed in unit Zil to channel i2 for translation to the receiving station H.

The receiving station comprises means coupled to the output terminals of channel i2 for utilizing the reference-signal components to derive the modulation components of the translated phasemodulated carrier signal. This means includes an amplifier and equalizer 30, such as an amplifier having a frequency-response characteristic selected to compensate for any nonuniform frequency-response characteristics of channel I2, coupled to output terminals [4, i l of the channel and frequency-selective means or filters 3|, 32 and 33 connected to the amplifier and equalizer 3B for individually selecting the received modulated carrier signal and each of the reference-signal components. Filters 3| and 32 are designed This means comprises renames :torhave passchandsewith. mean: frequencies corre --sponding:t0 individual 'onesof; the;reference:-sign'al components; and" sufficiently-wide; tolpass: the :band ofamplitude-modulation rcomponents: associated .With each such reference-signal compo- 1 nent. filter 33: has'-a'i pass. band having =a:.mean frequency which. correspondsto that of the car rier OOlliP-JlllltUG-f thephase-modulated signal andrlae pass hand: efiectivetto pass nthe l hand of 'phasel-"modulatiton components associated theregcoupled tofthe output-circuits of filterstl audit :for the'ipur-pose 10f leiiectively combining the separated reference-signal components. .putlcircuit ofi-mixer fid ivdesigned to select that upper :sideband :modulation component i which comprises'a'reference carrier signalhaving. a predetermined phased relation with reference to the carrier-signal generated-in oscillator fiat send- -ingtstation: l0,x but of twice the frequency. The ilimiter ofunit: s4 is provided; to remove all amplitude'modulation fromthis reference carrier sig-. xnal. r

'Inrorderuto utilize the derived :1 reference carrier signal for the purpose of detecting all of the phase-modulation components of the received phase-modulated carriersignal, it is desirable to :convert. the frequencyof the carrier component.

of-rconel'of thesesignals to that of the other. Accordingly, a frequent converter or multiplier 35 isprovided in'receiving station I I, coupled to the "outputcircuit of filter 33.

The output circuits of mixer 34 frequency converter 35ers coupled to input circuits of a phase-modulation detector 36 designed to derive .the desired phase-modulation. components =by effectively comparing the applied phase-modulated 'carrier signal andreferencfe carrier signal. #This detector maybe generally similar to that included in the phase-control system disclosed Fig. 1 of United States Letters Patent 2,231,?041, issued on February. 11, 1941, to Leslie F. Curtis. .Such a detector comprises of diodes to which the phase-modulated carrier signal is applied with like phase and to which the reference carrier signal is applied with opposite phase.

The cut .The unidirectional voltages developed in the load tected amplitude-modulation components may be .suppliedthereto for utilization in any. desired manner. For convenience of illustration, asingle utilizing circuit 38 has been shown. It will be understood that this unit includes circuit arrangements for utilizing'the modulation components derived in each detector 36 and 3?. In the most. general case, unit comprises two circuit arrangements individually designed to utilize the signaloutput of one of detectors Stand 3?.

In considering the operation of the described systermit will be seen that the angular velocity of the carrier signal applied by oscillator-l5 to -modulator l! is modulated in =-accordancewith the signals supplied by signaL-source liluor; ex-

signal.

cates tan infinitezxnumbers of modulation compotnents: or sidebands to tbe producedthrough= such modulating; process, the sideb ands being spaced kin; the: frequency; spectrum on L opposite sides 3 of thezwcarrier component. However, where the frequenc'yw deviation :of l the carrier signal is' large With *reference1 to the frequency of the. modulating signal; it. is found that the energy of those side 'band components. which are spaced from the carrier component by'an amount exceeding the maximum deviation ofxthe carrier signal is so small that such components .may :be neglected. Therefore, in such a case the. 'developed phaselnodulated signal may be deflnedes-having modulationcomponents predominantly in apredetermined band-of frequencies; which. band is determined by" the maximum deviation of the carrier Thus; for the=arrangement under considerationwhich employs suchl'ra mode ofrmodulation, the tphase-tmodulated signal produced in unit ll, asrepresented by the graphof Fig. 2, has

carrier. component of frequency f0 corresponding-to-theoperating frequency of oscillator 15 aud o band of phase-modulationcomponents having thedimiting frequencies of jo+Af and fo-Af,

.where Misthe maximumdeviation of the carrier signal. l

.z'Ilhe.carrier'signalfo supplied by oscillator 15 isalsoamplitude-modulated in modulator I9 with a modulating signal. having a frequency f1 .to produce upper and-lower 'sldeband components' having the frequencies fu-i-fi'and fu-h,

respectively. These components, being derived throughan amplitude-modulation process, have .such phase relations -with reference. to their carriertcomponentsfol-as to combine iniphase t herewith l and, it home, are 4 suitable reference-signal components for'providingla phase-reference signal representing the-absolute phase of the carrier signal foFmodulated in unit ll. Tofacilitate separating the-.phase-reference signal components-from thephasel-modulated carriersignal "at the receivingl station, the modulating fre- QUGHCYifU-lSvSOT chosen that the reference-signal components fe l-f1 and fo-f1have frequencies spaced from the carrier component In by equal and opposite increments of such 1 magnitude that the band of frequencies fo-Af to fo-l-Af containing the phase-modulation components islocated therebetween. lThisfrequency relation is clearly shownl'by'the graph of :Fig. 2.

1.The sdeveloped reference-signal components f0fr1 and fo-l-fnare individually amplitude-modulated in unit 2cm accordance with signals from sourceYEl, or inflaccordance with additionalinformationttowbe transmitted. The resulting sig- .naltoutputtofmodulator :20 comprises a pair of -amplitdde-modulatd reference-signal 1 compoapplied to channel I2 for translation to the receiver. This channel has a pass-band characteristic sufiiciently wide to pass the referencesignal components and their associated bands of modulation components a, b. At the receiving station these signals are selectively amplified in unit 30 to compensate for any nonuniform frequency-response characteristics of the translating channel and are thereafter individually separated by filters 3l-33, inclusive, their separation being facilitated by virtue of the aforementioned frequency relationships established at the sending station. The separated reference-signal components, upon being combined in mixer 3d, produce a phase-reference carrier signal having a predetermined phase relation with reference to the carrier signal of oscillator i5 included in the sending station, but of twice the frequency. This may be seen from the following consideration. The signals applied to mixer 312 include, among others, the carrier components of the amplitude-modulated carrier signals selected by filters 3i. and 32. Such components have the frequencies fo+f1 and fry-f1 and their sum frequency, obtained in the output circuit of unit Si, is 2ft, where f0 is the operating frequency of oscillator 55. Thus, the reference signal derived in unit 34 is harmonically related to the carrier component f0 of the received phasemodulated carrier signal and, specifically, the reference signal corresponds to the second harmonic of such carrier component. However, the separated phase-modulated carrier signal is doubled in frequency by frequency multiplier 35, so

that detector 3G, by comparing therewith the phase-reference carrier signals from mixer 34, is effective to derive all of the phase-modulation components for utilization in utilizing circuit 38. Further, the amplitude-modulation components of the particular reference-signal component fof1 selected by filters! are derived in detector 31 and are also supplied to circuit 38 for utilization in any desired manner.

It will be apparent that the aforedescribed system is especially suited for translating a-phasereference signal to be utilized in deriving the modulation components of a phase-modulated carrier signal. In the described arrangement, modulator 20 functions merely as an amplifier in the event that the only information to be translated between stations l0 and H comprises the signals from source I 6. ,7

It will also be apparent that a pair of amplitude-modulation detectors may be utilized in the receiving station II for individually deriving the amplitude-modulation components of each reference-signal component. This arrangement is particularly advantageous in those applications where there i an undesired frequency distortion in the signal-translating channel. In such a case, by combining the derived amplitude-modulation components from each of the detectors a compensation may be effected.

The described signal-translating system may be further extended by individually modulating the reference-signal components from unit I!) with additional information desired to be translated to receiving station I I. To accomplish this result, modulator 20 at sending station It may be replaced by a pair of amplitude modulators individually coupled to unit 19 through frequencyselective circuits so that one reference-signal component f0+f1 is applied to one such modulator while the other fo-Ji is applied to the other such modulator. It is then possible individually to couple a pair of different signal sources to the modulators, thereby separately to amplitudemodulate the reference-signal components with information to be translated. When the sending station is modified as herein suggested, corresponding modifications are necessary at receiving station H. In particular, an additional amplitude-modulation detector is required to be coupled to filter 32 so that the modulation compo nents of each received amplitude-modulated reference-signal component may be derived. However, in deriving the modulation components of the received phase-modulated carrier signal, the modified system operates substantially as hereinbefore described. The graph of Fig. 2 again illustrates the frequency relations to be maintained for the signals translated by the suggested modification. Accordingly, the expression means for modulating each of the reference-signal components in accordance with additional information to be translated as used in this description and in the appended claims is intended t include the specific arrangement of Fig. l and the aforementioned modification thereof.

In any case where information is translated between stations iii and H by amplitude modulation of the reference-signal components, it may be convenient to limit the percentage modulation to less than per cent. Where this operating condition is established, the signal outputs from filters 3i and 32 may be supplied to mixer 3 through limiter stages, adjusted to remove all amplitude modulation therefrom and thus supply to unit 34 nly signals having the frequencies fo-I-fi and fof1. Such an arrangement materially reduces the filtering problem otherwise presented when the signals applied to unit 34 comprise the amplitude-modulated reference-signal components.

In the foregoing description of receiving station 53 it was shown that mixer 34, by combining two reference-signal components having the frequencies f0+f1 and f0f1, respectively, produces the desired phase-reference signal having the frequency ZfO. This reference signal will be seen to be independent of thephase and freqency of the signal f1 utilized in generating the reference-signal components at the sending station ID. Thus, signal f1 may be variously modulated without affecting the desired phase-reference signal derived at the receiving station. Specifically, information may be translated by amplitude modulation of the reference-signal components, as particularly described in connection with the arrangement of Fig. 1, or by modulating the angular velocity of the reference-signal components in synchronism and in opposite senses, as in the arrangement of Fig. 3 presently to be described.

Fig. 3 represents a modification of the sending station ll] of Fig. 1 and corresponding components thereof are identified by like reference numerals primed. Sending station Iii comprises means for supplying a first signal and means for modulating the angular velocity of the first signal in accordance with information to be translated to develop a first modulated carrier signal having components predominantly in a first predetermined band of frequencies. Such means are provided by an oscillator l5 having a mean operating frequency f0, a signal source I6 representing the information to be translated, and a phase modulator ll interconnected as cor- 9 responding uni-ts of sending station i I of Fig. 1- described 1 above.

Sending station 1 also includes a signal source It for supplying a second signal and means for modulating the angular velocity of such second signal in accordance with. additional information to'be translated to develop a second modulated carrier signal havin components predominantlyin a second predetermined band of frequencies. This last-namedmeans comprises a phase modulator 24 having-input circuits individually coupled to signal source it! and to a source of phase-modulating signals 231epresenting such additional information.

A balanced amplitude modulator is is included in sendingstation H1 havingone input circuit coupled to oscillator I and another input circuit coupled to phase modulator 2 L Thus, unit l9- comprises means for amplitude-modulating the first signal, i. e. the signal from oscillator I 5", with themodulated carrier signal of.

modulator i i to develop only a pair of angularvelocity-modulated signals having predetermined phase relations with reference to the aforesaid first signal. A combining amplifier 22" serves to apply the phase-modulated carrier signal pro ducedin unit I? and thepair of phase-moclu lated signals produced in-unit E9 to a signaltranslating channel! for translation to the receivingstation H.

Receiving station: H, when the above-described sendingystation I is utilized in the signal-translatingsystem of the invention, may be substantiallyas represented in Fig. '1. However,- it will be necessary to substitute a phase-modulation detectorior unit 37 thereof and filters 3i, 32must have band widths sufficiently wide to accommodate a band of. frequenciescontaining the. predominant modulation components of one of the above-mentioned pair of modulated sigsid eration, modulator. I9: produces, as reference signals a pairof angular-velocity-modulated signals having predetermined phase. relations .with reference to. th'e.= carrier. signal J ft supplied byoscillator. I 5 and having modulation componentscorresponding to those of the: modulated carrier it has; the frequencyfo and the modulating signals supplied from -unit 24 maywbe represented as fi-l- Af'. The resulting -modulation productsobtained from the output circuit ofunit l9 are:

jo-l-(fiiAfiH and foeeifri-Af' (1) This. expressionmaybe rewritten as:

f0+TfT and iii-him? (2).

It1willcbe1apparent fromexpression (2.) that the pair: of :m'odulatedifisignals; utilized ;,in the instant modification, of the. invention. to translate a phaserreference tocrece'iver station ll, areangunals produced in modulator. H9 at sendingsta tion Hi1.

In considering the operationofi the signal functions as an amplifier; and balanced modu r lator l9 produces reference-signal; components having the frequencies =Jo+f1 and J'0f1. These signals are translated over channel l2 to the receiving station it where-they are utilized to derive the modulation components of the transe latedl modulated carrier signal. This operation of stations Hi" and ii is precisely as described hereinbeiore in connection with the arrangement of Fig. 1.

When signals from source 23 are also; to be translated, modulator 2 8 develops a secondangular-velocity-modulated carrier signal; Fig. 312; having a carrier componentofirequency f1 and. modulation components predominantly; in a sec- 0nd predetermined band of. frequencies having the limiting values oil? f1+Af' and h-Af, Where M" is the maximum deviation of signal ii in such modulation. In this respect the. operation of modulator E lis similar to that of modulator l'l. However, iorthexoperating conditionsunder confi /11M? tion components .of the. pair 1 ofmodulated signals larevelocityemodulated; in synchronism and in: opposite; sensesl. IhLWill :berfurther apparent that the sum frequencies of such modulated signals is equaljto 2fo. Whic'his harmonically related; to. both thezsignal producediby.:osci1lator. E and thecarriera-component-of the modulated carrier signal developed inwm-odulatonll'r. w Thusythe signal :transmittedtoreceiving statioml lifro'm station; It. -for-the. assumed condia tions, is as represented by the graph of Fig. 3c.- Inorder thattha several signals may be conveniently separated, atv the receiving station, the.

frequenciesof the first and second signals sup.- plifedjby unitselii' and I85, respectively are. so chpsenland .theirangulan-velocity modulation is such that thepredeterminedband .of frequencies foiAf. contairlirigw the predominant modulation.

components produced in unit [1' islocated the frequency spectrum between thepdiiferent indi-. and.

vidual; bands of; frequencies jo-l-hiAj.

containingthe predominant modulafrom. modulator, l9. The operation of the re.- c eiving station in deriving, the. modulation. components,.from thetranslatedsignals is substantially as .describedin. connection. .with the arrangement (of Fig. .1.

A. further, modification of the. invention is representedginFig. 4.,which comprises. a sending station, E01. having. a: construction generally similar; to. that ofsending station I; already described,- identified.-

comprises a 1 pair; of; predeterminedmhase spaced therefrom in the. frequency spectrum by equal and j opposite values. y Suchflmeans comprise abalanced; amplitude modulator; I961 having one;

input circuit coupledgto: oscillatori l5." and another. input circuit coupled-ltd.arsignalsource cults.gindividuallyr'coupledsto balanced modulator I9 andzztoga si nal source: [6. representinginformation toubfertranslated;constitutesrneans for modulating "the. angular. velocity of the second named signal in accordance with information to be. translated: to develop a pair of modulated corresponding parts thereof, being. bylike reference numerals double. primed. Sending; station 107; includes anoscillater! 5?. fomsupp lyinga first:signal of frequency fpand; means forsHPPlyinga second; signal which signal components having relationswith referencevto the first-named signal and being; individually carrier signals, described more particularly hereinafter. A combining amplifier 22" has input circuits coupled to modulator l1" and to oscillator l5", being provided as a means for applying to a signal-translating channel 12" the pair of modulated carrier signals developed in modulator ll" and a phase-reference signal obtained from oscillator l5".

Receiving station H of Fig. 1 may also be utilized with sending station I to complete the signal-translating system. However, in such an arrangement the amplitude-modulation detector 31 will not be required at the receiving station and filter 33 may be sharply selective to the frequency f of oscillator l.

In the arrangement of Fig. 4, a signal from oscillator l5" having the frequency f0 and a signal from source It" having the frequency ii are modulated in unit It" producing in the output circuit thereof a signal which comprises a pair of components having the frequencies, respectively, fo+f1 and Jo-fr. Since these components are produced through an amplitude modulation process they have predetermined phase relations with reference to the signal from oscillator it as mentioned hereinbefore and the frequency relationships of such signals are as indicated by the graph of Fig. 4a. The signal components from modulator 19 are phasemodulated in unit ll" information to be translated to develop a pair of angular-velocity-modulated carrier signals. These modulated carrier signals may be defined (fo+f1):tAf; (fof1)iAf (3) Where A) represents the maximum deviation of each carrier component. It will be apparent from expression (3) that the carrier signals are angular-velocity modulated in synchronism and in the same sense and therefore their sum frequency, as obtained in a modulator, is equal to ZfoiZAf. In other words, by combining such modulated carrier signals a third angularvelocity-modulated carrier signal is obtained which has a carrier component harmonically related to the signal from oscillator I5" and having modulation components which correspond to the modulation components of each of the pair of modulated carrier signals produced in unit H. In order that the pair of modulated carrier signals translated from sending station It" to receiving station I I may be readily separated and then modulated at the receiving station to derive the above-mentioned third angular-velocitymodulated carrier signal, the frequency relationships indicated by the graph of Fig. 4a must be established. In particular, the angular-velocity modulation in unit ll" must be such that each modulated carrier signal obtained therefrom has predominant modulation components within an individual modulation band located only in a portion of the frequency spectrum which is adjacent its carrier frequency. Also, the width of one modulation sideband of each of the pair of modulated carrier signals is to be less than the separation between the frequency f0 and the particular carrier frequency.

The operation of receiving station H in combining the translated pair of modulated carrier signals to derive the aforementioned third angular-velocity-modulated carrier signal and the manner of utilizing the reference signal of frequency .fo translated from oscillator I 5 will be apparent.

Fig. 5 represents a still further modification of in accordance with a signal-translating system in accordance with the invention, this modification being generally similar to that of Fig.4 and corresponding components are identified by like reference numerals triple primed. This modification includes an oscillator 15" for supplying a first signal, a phase modulator l'i' and a source of phase-modulating signals lfi' representing information to be transmitted, interconnected as described in connection with the arrangement of Fig. l to develop a first modulated carrier signal having predominant modulation components in a predetermined band of frequencies.

Sending station 10 further includes means for amplitude-modulating the aforementioned first modulated carrier signal to develop a pair of angular-velocity-modulated signals described more particularly hereinafter. Such means consists of a balanced amplitude modulator IQ' having an input circuit coupled to phase modulator ll and another input circuit coupled to a signal source lil which supplies a second, or modulating, signal of frequency f1. Additionally, station it is provided with means for supplying a third signal having predetermined phase and frequency relations with reference to the aforementioned first signal, namely, that applied to modulator l'l from oscillator l5'. It is preferred that these signals have substantially the same phase and frequency characteristics and, accordingly, the third signal is derived from a second output circuit of oscillator 15 as illustrated. Such third-named signal, as well as the pair of modulated signals produced in modulator l9, is applied to a signal-translating channel IZ by way of a combining amplifier 22' having input circuits individually coupled to units i5' and l9'.

Receiving station ll of Fig. 1 may be utilized in connection with the described sending station 3' to complete a signal-translating system, it being only necessary to modify the receiving station as above mentioned in connection with the Fig. 4 embodiment.

In considering the operation of the Fig. 5 arrangement, reference is made to the graphs of Figs. 5a and 5b. The carrier signal of frequency in supplied from oscillator l5' to modulator 17 is phase-modulated in accordance with information to be translated to develop a first angularvelocity-modulated carrier signal having predominant modulation components in a predetermined band of frequencies. This modulated signal, which is represented graphically in Fig. 5a, is amplitude-modulated in unit 19 with the signal supplied from source l8'. There results from such modulation a pair of angularvelocity-modulated carrier signals having predetermined phase relations with reference to the modulated carrier signal from modulator ll and having modulation components corresponding to those of the modulated carrier signal from ll but contained in different individual predetermined bands of frequencies as indicated in Fig. 5b. This may be clearly understood from the following:

The signals applied to unit I9 to be modulated may be expressed as foiAf while the modulating signal may be defined as f1. The modulation products derived from unit lll are:

Itlwill be apparent from a comparison: ofexpressions (3) and (5);that the pair of modulated carrier signals developed in the arrangements of Figs. 4 and 5-are identical. Hence, thereference signal from oscillator I5 which is translated along with such pair of modulated carrier signals maybe utilized at thereceiving station as previously described for deriving the desired modulation components. However, the frequency rela. tionships represented by the: graph: of Fig. 5b must be maintained at the sending station in order thatfsuch signalsmay be conveniently separated. This may be achieved by-selecting the frequencyof modulating signal f1 suchwthat the signal it from oscillator, l5 isylocated in the frequency spectrum between :the. different predetermined bandsofjfrequencies [(fn-tflljznfl and Ufa-41) inf] containing the predominant 1nod-' ulation components ofeachwof :the1pair -1"- modus lated signals; respectively.

Inasmuch as the arrangementsof Figs. 4 and operate-:in substantially the same manner and translate identical signals, the expressions i means foreffectivelysupplying a secondsignal comprising :a pair :of signal components. and means for modulating'the angularpvelocity of said second signal to develop, ;a pair of modulated carriertsignalsi as usedin the specification and in the appended claims are intendedto include both such arrangements l Tosimplify-the explanation, the reference signal transmittedtfrom thesending station in both the iFigS; 4 and 5 embodiments has 1 been disclosed asan-unmodulated signal of frequency in. If desired; theautility .of either arrangement may x be enhanced :by, translating additional information as tamplitude modulation on suchreference. sig:

nal. Sotlong. as the-percentage modulation is frequency discrimination; proposed by' C. F. Shaeffer; andxdescribed inthe Proceedings of the I. R.E.-, vol. No. 8, August, 1942, page 365-367,

inclusive. When adapted to such. a system, the reference signal derived at the receiving station may be utilized asthe reference oscillations supplied. to' the zero-beat frequency-discriminator system... Such a frequency-modulation system has the advantages that the system utilizes in the discriminator no resonant 1 circuits which may be come detuned; that the reference oscillations determine the balance or center. frequency ofthe discriminator; thereby facilitating itsadjustment; andlthat the linearity of the system is improved.=

While there have been described what are at present considered to be the preferred embodi ments of this invention, it will be obvious tothose skilled in the art thatvarious changes and'modifications may be made therein without departingfrom the invention, and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fallwithin the true spirit and scope of the invention,

What is claimed is 1. A signal-translating system comprising, means for. supplying a first signal, means for effectively supplying a secondsignal comprising a pair of signal components having predetermined trum which is adjacent its carrier frequency; the

limited toless thanl00 percent, the carrier component, requiredas a phasereferencei signal at:

thereceiving station may be derived through the use. of a limiter: stage, as hereinbeforesuggested.

spaced. therefrom in the frequency SpectrumJby equal and opposite ,yalues; Also, in each case, the

system includes means: for modulating the angular.velocity of onewof the aforesaid first. and secondtsignals in accordance with the. information to be transmittedto develop a-modulatedcarrien signal having predominant modulationcompo nents within a modulation :band; located onlyin a.

portion of the frequency spectrum which is ad-. jacent its carrier: frequency, the: width of one modulation sideband thereof -beingleSs3than one of the aforementioned values. Further, each system comprises a'signal-translating channel, and

means for applying-to that channel thevrnodue lated lcarriersignal and 'the other of ,the aforesaid first .and second signals.

Fora specific application of a phase modulation system in accordance with the teachings of this invention, reference may be had to copendingapplication serial No. 503,069, filed concurrently herewith in the name of Bernard D. Loughli and assignedto the sameassignee as the present invention. Furthermore, the signaltranslating system is especially suitedfor application toa frequency modulation systemof the'type which employs a so=called= zero-beat method of nals to said input terminals, andemeans coupled -tosaid output terminals for utilizing said modulated carrier signal and saidother one of said first and second signals to derive said modulation components.

2.1A signal-translating system comprising,

.means for supplying a first signal, mean for effectively supplyinga second signal comprising a pair of signal components having, predetermined phase relations with reference to said first signal and being individually spaced therefrom in the frequency spectrum by equal and opposite values, means for modulating the angular velocity of one of said firstand second signals in accordance with information to be transmittedto develop a modulated carrier signal having predominant modulation components Within a modulation band located only in a portion of the frequency spectrum which is adjacent its carrier frequency, the Width of onemodulation sideband thereof be ing less than one of said 'values,a signal-trans lating channel having input and output terminals, means for applying said modulated carrier signal and the other one of said first andsecond signals to saidinput terminals, frequency-selective means coupled to saidoutputterminals for individually separating said modulated carrier meansdon supplying-a first signal, means foreffectively supplying a second signal comprising a' pair of signal components having predetermined phase relations with reference to said first signal and being individually spaced therefrom in the frequency spectrum by equal and opposite values, means for modulating the angular velocity of one of said first and second signals in accordance with information to be transmitted to develop a modulated carrier signal having predominant modulation components within a modulation band located only in a portion of the frequency spectrum which is adjacent its carrier frequency, the width of one modulation sideband thereof being less than one of said values, a signal-translating channel having input and output terminals, means for applying said modulated carrier signal and the other one of said first and second signals to said input terminals, frequency-selective means coupled to said output terminals for individually separating said modulated carrier signal and said other one of said first and second signals, means for deriving from the separated other one of said first and second signals a reference signal having predetermined phase and frequency relations with respect to the carrier component of the separated modulated carrier signal, and means for utilizing said reference signal and said separated modulated carrier signal to derive said modulation components.

4. A signal-translating system comprising, means for supplying a first ignal, means for effectively upplying a second signal comprising a pair of signal components having predetermined phase relations with reference to said first signal and being individually spaced therefrom in the frequency spectrum by equal and opposite values, means for modulating the angular velocity of one of said first and second signals in accordance with information to be transmitted to develop a modulated carrier signal having predominant modulation components with a modulation band located only in a portion of the frequency spectrum which is adjacent its carrier frequency, the width of one modulation sideband thereof being less than one of said values, a signal-translating channel having input and output terminals, means for applying said modulated carrier signal and the other one of said first and second signals to said input terminals, frequency-selective means coupled to said output terminals for individually separating said modulated carrier signal and said other one of said first and second signals, means for deriving from the separated other one of said first and second signals a reference signal of substantially the same phase and frequency as the carrier component of the separated modulated carrier signal, and means for utilizing said reference signal and said separated modulated carrier signal to derive said modulation components.

5. A signal-translating system comprising, means for supplying an angular-velocity-modulated carrier signal having modulation components determined by information to be translated and predominantly in a predetermined band of frequencies, means for supplying a pair of reference-signal components having predetermined phase relations with reference to the carrier component of said signal, the frequencies of said reference-signal components being spaced in the frequency spectrum from said carrier component by equal and opposite increments of such magnitude that said predetermined band of frequencies is located therebetween, a signal-translating channel having input and output terminals, means for applying said modulated carrier sisnal and said reference-signal components to said input terminals, frequency-selective means coupled to said output terminals for individually separating said modulated carrier signal and each of said reference-signal components, means for combining the separated reference-signal components to derive a reference carrier signal which is harmonically related to the carrier component of the separated modulated carrier signal, and means for utilizing said reference carrier signal and the separated modulated carrier signal for deriving said modulation components.

6. A signal-translating system comprising, means for supplying an angular-velocity-moolulated carrier signal having modulation components determined by information to be translated and predominantly in a predetermined band of frequencies, means for supplying a pair of reference-signal components having predetermined phase relations with reference to the carrier component of said signal, the frequencies of said reference-signal components being spaced in the frequency spectrum from said carrier component by equal and opposite increments of such magnitude that said predetermined band of frequencies is located therebetween, a signal-translating channel having input and output terminals, means for applying said modulated carrier signal and said reference-signal components to said input terminals, frequency-selective means coupled to said output terminals for individually separating said modulated carrier signal and each of said reference-signal components, means for combining said separated reference-signal components to derive a reference carrier signal which is harmonically related to the carrier component of the separated modulated carrier signal, a frequency converter, means for applying one of said carrier signals to said frequency converter to convert the frequency of the carrier component of said one carrier signal to that of the other, a detector, and means for applying the carrier signal of converted frequency and said other carrier signal to said detector to derive said modulation components.

7. A signal-translating system comprising, means for supplying an angular-velocity-modulated carrier signal having modulation components determined by information to be translated and predominantly in a predetermined band of frequencies, means for supplying a pair of reference-signal components having predetermined phase relations with reference to the carrier component of said signal, the frequencies of said reference-signal components being spaced in the frequency spectrum from said carrier component by equal and opposite increments of such magnitude that said predetermined band of frequencies is located therebetween, a signal-translating channel having input and output terminals, means for applying said modulated carrier signal and said reference-signal components to said input terminals, frequency-selective means coupled to said output terminals for individually separating said modulated carrier signal and each of said reference-signal components, means for combining the separated reference-signal components to derive a reference carrier signal corresponding to the second harmonic of the carrier component of the separated modulated carrier signal, a frequency doubler, means for applying said separated modulated carrier signal to said frequency doubler to double the frequency thereof, adetector, and means for applying said reference carrier signal and the double-frequency rive said modulation components.

signal-translating system, comprisi g,

imwris for supplying an angular-ivelocityEmodii Ha ted carrier signal having modulationcbmponcnts determined by 'informationto' be trans erence signal components having predetermined 'Dhase relations with reference to-thecar'rie'r co 1-1 ponent' of said signalgmeans fo'rmodulatinge of said reference-signal componentsin accord-f ance with additional information to beftransflated thereby to develop afpair of modula d reference signal components having: modulat on components in differe j t 1 predeteimined bands oi, frequencies, the frequenciesof said reference- 1 nal components heingfspaceld infthrr spectrum by equal ando'pposite inc e said carrier componentand the re ue saidmodulatidn components cl U r signal components being such that sa named band of frequencies isiocatedwet said different predeterminedhands of frequencies; a Signal-translating channel navirlginput and nu'tput terminals, means for applying j'saidfmodu-j Hated carrier signal and said modnlated refer ence-signal components to said input terminals,

- frequency-selective means coupled to said output terminals for individually separating saidmodulated carriersignal and each of said modulated reference-signal components, means coupled to said frequency-selective means for utilizing the separated signals to derivesaid modulati n omponents of said modulatedcarrier sigma I ditional means coupled to said frequency-selective means for deriving said modulatiori comp he is of at leastone' of said modulated reference components."

9. A signal-translating system pin nsing;

meansfor supplying a firstsignal, means for ef fectively'supplying a second signalfcornpr :a a pair of signal components having predete ned' phaserelations with reference to said firstfnarhed: signal and being individually spaced therefrom in the frequency spectrum by equaland opposite values; means for modulating the angular elocity of said second signal i'n'accordance withinfo m tion to be translated to develop a pair of lated carrier signals each having pred modulation component's ivithin fan modulation band located only in a portionor the frequency spectrum which isadjacent its carrier frequency, the Width of one modulation sidehand of eachofsaid pairof modulated carrier signals being less than one of said values, a signal-trans lating channel having input and output termi-c nals, means for apply g said first-na fi a and said pair of modulated carrier signals to said input terminals, frequency-selective means coupled to said outputterminals for individually separating said first-named signal andeach oi said pair of modulated carrier signals, means for com bining the separated modulated carrier signals to derive athird angular-velocity inodulated car'- rier signal having a carrier component harmon ically related to said first-named signal and naying modulation components corresponding to said modulation components of each of saidlpair c-f modulated carrier signals, and "means for an;

lizingthe separated first-namedsignalto derive said, modulation components of said mo gu lated carrier signal; c a

10 A signal-translating system c rising,

means for-supplying a first'signal means a:

ni ro en;

lated and predominantly ina p'redeterminedhaiid bffrequencies, meansfor supplying a pair of reffee vely second "signal comprising a pa of signal components having predetermined th reference to said first-named ing 'idividually spaced therefrom in cans tor modulatingythe angular ve of said secondsignal in accordance with information to be translated to develop a pair f o odulated carrier signals'e'achhaving pre- 110 dominant mcdu at bn components within indi- Vldllal modulation bands located only in a portion of the nq my spectrum which 3 is adjati ti 'qarfie tirt acy th idt o one m l lat" ii side'band oi eachoisaid pair of modulated are siee lsfbine th ac said a u a signal anslating channel having input and output terminalsjmeans for applying saidfirst named 'gnal and said pair of modulated carrier Q Said in u te mi s f lie l i eciiyje me ns cmipieq1pc said output terminals forindividu lly separating said first-named signalanjdfeach of said pair of modulated carrier signals; means forijccmhining. the separated mo u'lat carrier signals to derive a third an g'ular -velocityodulated carrier signal having a carrierccmponent which corresponds to the second harmonic ofsaidfirst-named signal and hav-I ing modulation components corresponding to said modulation components of each of said pair of modulated carriersignals, and means for utilizthe separated first named signal: to derive fodulation components of said third moduk ierl e a i r '11. signal-translating system comprising,

means l for'supplying a'first signal, means for effectively supplyinjg a second signalcomprising a loi signal iiipon'ents having predetermined ithj reference t osaid. first-named pectrunil by'equal and opposite cans aonmodulating the angular velocoffsaid second signal in accordance withinformation to be translated todevelop a pair of modulated carrier signals each havingpredoininant lrnodulation components within an individual modulation band located only in a portion of tliePfreduency spectrum which is adjacent its carrier frequency, the Width of one modulation side": hand of each of said pair of modulated car rier signals being less than one ofsaid values, a signal-translating channel havinginput and output terminals, means for applying said firstnamed signal andsaid paifof modulated carrier signals tosaid input terminals, frequency-selec 55 tive means coupled toifsaid output terminals for individually separating said first-named signal and each of said pair of modulated carrier signaisginesnsj for combining the separated modulated' carrier signals to derive av thirdangulan 60 velocity-modulated; carrier signal having a car rier component which :correspondsto the second harmonicof said first-named signal and having modulation componentscorresponding to said i modulation components of each of saidpair of modulated carriersignals, means for doubling the frequency of the s'eparated first-named signal to d eri Ve a reference signal of substantially I the ame p ase and frequency as the carrier compc e t s dt i d l d arri r Signal, a i

t liqri an me n fo su plyin a qfete i n e s idq rs simulate a e slgnel i sai etectorto derive said modul t o omp i 1 1 vaIals g l-sr m ys em compnslilg pp ng st ignal, means for ef-.

edu ncy spectrum py]equa1and opposite fectively supplying a second signal comprising a pair of signal components having predetermined phase relations with reference to said first signal and being individually spaced therefrom in the frequency spectrum by equal and opposite values, means for modulating the angular velocity of one of said first and second signals in accordance with information to be transmitted to develop a modulated carrier signal having predominant modulation components Within a modulation band located only in a portion of the frequency spectrum, which is adjacent its carrier frequency, the width of one modulation sideband thereof being less than one of said values, a Signal-translating channel, and means for applying to said channel said modulated carrier signal and the other one of said first and second signals.

13. A signal-translating system comprising, means for supplying a first signal, means for effectively supplying a second signal comprising a pair of signal components having predetermined phase relations with reference to said first signal and being individually spaced therefrom in the frequency spectrum by equal and opposite values, means for phase-modulating one of said first and second signals in accordance with information to be transmitted to develop a phasemodulated carrier signal having predominant modulation components within a modulation band located only in a portion of the frequency spectrum which is adjacent its carrier frequency, the width of one modulation sideband thereof being less than one of said values, a signal-translatingchannel, and means for applying to said channel said phase-modulated carrier signal and the other one of said first and second signals.

14. A signal-translating system comprising, means for supplying a first signal, means for effectively deriving from said first signal a second signal comprising a pair of signal components having predetermined phase relations with reference to said first signal and being individually spaced therefromin the, frequency spectrum by equal and opposite values, means for modulating the angular velocity of one of said first and second signals in accordance with information to be transmitted to develop a modulated carrier signal having predominant modulation components within a modulation band located only in a portion of the frequency spectrum which is adjacent its carrier frequency, the width of one modulation sideband thereof being less than one of said values, a signal-translating channel, and means for applying to said channel said modulated carrier signal and the other one of said first and second signals.

15. A signal-translating system comprising, means for supplying an angular-velocity-modulated carrier signal having modulation components determined by information to be translated and predominantly in a predetermined band of frequencies, means for supplying a pair of reference-signal components having predetermined phase relations with reference to the carrier component of said signal, the frequencies of said reference-signal components being spaced in the frequency spectrum from said carrier component by equal and opposite increments of such magnitude that said predetermined band of frequencies is located therebetween, a signal-translating channel, and means for applying to said channel said modulated carrier signal and said referencesignal components.

16. A signal-translating system comprising,

means for supplying a first signal, means for modulating the angular Velocity of said first signal in accordance with information to be translated to develop a modulated carrier signal having components predominantly in a predetermined band of frequencies, means for supplying a second signal having predetermined frequency and phase relations with reference to said first signal, means for amplitude-modulating said second signal to develop reference-signal components comprising upper and lower sideband components of amplitude modulation, the frequency of said second signal and the modulation free quency of said amplitude modulation being such that said predetermined band of frequencies is located between said reference-signal components in the frequency spectrum, a signal-trans latingchannel, and means .for applying to said channel said modulated carrier signal and said reference-signal components. 7

17. A signal-translating system comprising, means for supplying a first signal, means for modulating the angular velocity of said first signal in accordance with information to be translated to develop a modulated carrier signal having components predominantly in a predetermined band of frequencies, means for supplying a second signal of substantially the same phase and determined band of frequencies is located between said reference-signal components in the frequency spectrum, a signal-translating channel, and means for applying to said channel said modulated carrier signal and said reference-signal components.

18. A signal-translating system comprising, means for supplying a carrier signal, means for modulating the angular velocity of said carrier signal in accordance with information to be translated to develop a modulated carrier signal having components predominantly in a predetermined band of frequencies, means for amplitude-modulating said carrier signal to develop reference-signal components comprising upper and lower sideband components of amplitude modulation, the modulation frequency of said amplitude modulationbeing such that said predetermined band of frequencies is located between said reference-signal components in the frequency spectrum, a signal-translating channel, and means for applying to said channel said first-named modulated carrier signal and said reference-signal components.

19. A signal-translating system comprising, means for supplying a carrier signal, means for modulating the angular velocity of said carrier signal in accordance with information to be translated to develop a modulated carrier signal having components predominantly in a predetermined band of frequencies, means for supplying a modulating signal of a predetermined frequency, a balanced amplitude modulator, means for applying said carrier signal and said modulating signal to said modulator to produce reference-signal components comprising upper and lower sideband components of amplitude modulation, the frequency of said modulating signal being such that said predetermined band of frequencies is located between said reference-signal components in the frequency spectrum, a signal tially the same phase and frequency as said first signal, a signal-translating channel, and means for applying to said channel said pair of modulated signals and said third signal.

26. A signal-translating system comprising, means for supplying a first signal, means for modulating the angular velocity of said first signal in accordance with information to be translated to develop a first modulated carrier signal having predominant modulation components in a predetermined band of frequencies, means for supplying a second signal, mean for amplitudemodulating said first modulated carrier signal with said second signal to develop a pair of angular-veloci-ty-modulated signals having predetermined phase relations with reference to said first modulated carrier signal and having modulation components corresponding to those of said first modulated carrier signal but contained in different individual predetermined bands of frequencies, the frequency of said second signal being such that said first signal is located in the frequency spectrum between said different individual predetermined bands of frequencies, a signal-translating channel, and means for applying to said channel said pair of moduated' signals and said first signal.

27. In a system for translating a composite signal including a first signal and a second signal which includes a pair of signal components having predetermined phase relations with reference to said first signal and individually spaced therefrom in the frequency spectrum by equal and opposite values, one of said first and second signals being angular-velocity-modulated in accordance with information to be translated so as to provide a modulated carrier signal having predominant modulation components within a modulation band located only in a portion of the frequency spectrum which is adjacent its carrier frequency, the width of one modulation sideband thereof being less than one of said values, a receiver comprising, a pair of input terminals for receiving said composite signal, frequencyselective means coupled to said terminals for individually separating said modulated carrier signal and said other one of said first and second signals, and means coupled to said frequencyselective means for utilizing the separated si nals to derive said modulation components.

28. In a system for translating a composite signal including a first signal and a second signal which includes a pair of signal components having predetermined phase relations with reference to said first signal and individually spaced therefrom in the frequency spectrum by equal and opposite values, one of said first and second signals being angular-velocity-modulated in accordance with information to be translated so as to, provide a modulated carrier signal having predominant modulation components within a modulation band located only in a portion of the frequency spectrum which is adjacent its carrier frequency, the width of one modulation ideband thereof being less than one of said values, a receiver comprising, a pair of input terminals for receiving said composite signal, frequencyselective means coupled to said terminals for individually separating said modulated carrier signal and said other one of said first and second signals, means for deriving from the separated other one of said first and second signals a reference signal having predetermined phase and frequency relations with reference to th carrier component ofthe separated modulated carrier signal, and means for utilizing said ref-- erence signal and said separated modulated carrier signal to derive said modulation components.

29. In a system for translating a composite signal including a first signal and a second signal- Which includes a pair of signal components having predetermined phase relations with'reference to said first signal and individually spaced therefrom in the frequency spectrum by equal and 010- posite values, one of said first and second signals being angular-velocity-modulated in accordance with information to be translated so as to provide a modulated carrier signal having predominant modulation components within a modula-- tion band located only in a portion of the frequency spectrum which is adjacent its carrier frequency, the width of one modulation side'band thereof being less than one of said values, a re-- ceiver comprising, a pair of input terminals'forreceiving said composite signal, frequency-selective means coupled to said terminals for individually separating said modulated carrier signal and said other one of said first and second signals, means for deriving from the separated other one ence signal and said separated modulated carriersignal to derive said modulation components.

30. In a system for translating a composite signal which includes a first signal comprising an angular-velocity-modulated carrier signal having modulation components determined by information to be translated and predominantly in a predetermined band of frequencies and a second signal including a pair of reference-signal compo nents having predetermined phase relations with reference to the carrier component of said first signal, the frequencies of said reference-signal components being spaced in the frequency spectrum from said carrier component by equal-and opposite increments of such magnitude thatsaid predetermined band of frequencies is located therebetween, a receiver comprising, a pair of input terminals for receiving said composite signal, frequency-selective means coupled to said terminals for individually separating said modulated carrier signal and each of said referencesignal components, means for combining the separated reference-signal components to derive a reference carrier signal which is harmonically related to said carrier component of said modulated carrier signal, and means for utilizing said reference carrier signal and the separated modulated carrier signal for deriving said modulation components.

31. In a system for translating a composite signal which includes a first signal comprising an angular-velocity-modulated carrier signal having modulation components determined by infor mation to be translated and predominantly in a predetermined band of frequencies and a second signal including a pair of reference-signal components having predetermined phase relations with reference to the carrier component of said first signal, the frequencies of said reference-signal components being spaced in the frequency spectrum from said carrier component by equal and opposite increments of such magnitude that said predetermined band of frequencies is located therebetween, a receiver comprising, a pair of in put terminals for receiving said composite signal,

frequency-selective means coupled to said termi.

reference-signal components to derive areference,

carrier signal which is harmonically related to said carrier component of said modulated carrier signal, a frequency converter, means for applying oneof said carrier signals to said frequency converter to convert the frequency of the carrier component of said one carrier signal to that of the other, a detector, and means for applying the carrier signal of converted frequency and said other carrier signal to said detector to derive said modulation components.

32. In a system for translating a, composite signal which includes a first signal and a second signal comprising a pair of angular-velocity-modulated carrier signals the carrier components of which have predetermined phase relations with reference to said first signal and are individually spaced therefrom in the frequency spectrum by equal and opposite values, said pair of carrier signals each including predominant modulation components within an individual modulation band located only in a portion of the frequency spectrum which is adjacent its carrier frequency, the width of one modulation sideband of each of said pair of carrier signals being less than one of said values, a receiver comprising, a pair of input terminals for receiving said composite signal, frequency-selective means coupled to said terminals for individually separatin said first signal and each of said pair of modulated carrier signals, means for combining the separated modulated carrier signals to derive a third angular-velocitymodulated carrier signal having a carrier component harmonically related to said first signal and havin modulation components corresponding to said modulation components of each of said pair of modulated carrier signals, and means for utilizing, the separated first signal to derive said modulation components of said third modulated carrier signal.

BERNARD D. LOUGHLIN. 

